Column leaching experiments were conducted to simulate in-situ leaching processes and to provide information on the mechanisms and extent of copper recovery, acid consumption, and chemical composition of recycled raffinate. Two 1.52-meter by 0.30-meter columns, each loaded with approximately 150 kilograms of copper oxide ore from the Florence porphyry copper deposit, were leached with a dilute sulfuric acid solution for 84 days. Computer simulation of the saturation state and aqueous mass transfer of predominant elements during the column tests was performed using EQ3NR, an aqueous solution speciation-solubility modeling code and the geochemical mass balance modeling code NETPATH. These modeling codes were used to quantify the amount of minerals dissolved and precipitated in the columns during the column leaching experiments. NETPATH mass balance models containing Cu-montmorillonite and chrysocolla as sources of copper match observations of pre-leach material. Cu-montmorillonite contributed 55% and 34% of the dissolved copper in the columns effluent.